If you have class C rentals, I like to use Traffic master Grip Strip Water Resistant Luxury Vinyl Plank Flooring.

This means, no electricity and no water as the well can't pump - which also translates to you get one more flush on each toilet and then you are done.  

They know the tenant base, median rents of different areas, how much to increase rent each year, ranges of repair costs (ex: tenant calls and says AC isn't working, no hot water, faucet is leaking, the HVAC system goes out).

To manage this, find the average electricity, water, and gas usage in your area.

Maybe find out you didn't replace cathodes, and the water is harder there.

Currently, there's only one water meter for the entire duplex, and historically, I've been responsible for paying the water bills every month.However, I believe it's time to transition to a system where the water bill is split between the two tenants.

Rain water used to sit in back yard and crawlspace.

It's a drainage ditch. 

Tenant now requests a water softener (we live in a very hard water area) due to clothes not being clean, stains, etc.

You should be calculating Cap Ex for all long term items that will need replacement at some point - appliances, roofs, ac, water heater, etc.